Some wireless communications networks adopt orthogonal frequency-division multiplexing (OFDM) or orthogonal frequency-division multiple access (OFDMA) to take advantage of the immunity to multi-path fading and impulsive noise that these two methods provide. One of the characteristics of an OFDM or OFDMA system is that multiple carriers transmit information simultaneously. Due to this characteristic, an OFDM or OFDMA system is more sensitive to synchronization errors that occur in a preamble detection process, compared with a wireless communications network that employs a single carrier.
Synchronization errors in preamble detection include timing position errors and carrier frequency offset errors. The synchronization errors of the front-end of an OFDM receiver create a carrier frequency offset and a significant timing error that degrade the performance of an OFDM system. A carrier frequency offset results in a loss of orthogonality while a timing error could degrade the signal-noise-ratio (SNR) of the system. As a result, intra-symbol or inter-symbol interference occurs.
The algorithms for estimating a timing position and a frequency offset jointly are computationally intensive. To reduce the demand on the resources required for computation, the estimation of a timing position and that of a frequency offset are executed in separate stages. In general, the estimation of a timing position takes place before that of a carrier frequency offset.
The accuracy of timing position estimation has a major effect on the estimation of a carrier frequency offset. Specifically, when a timing position error is larger than the cyclic prefix (CP) length, OFDM or OFDMA no longer works correctly.
What is desired is a method and system with low complexity for improving timing position estimation and reducing timing position errors to be within −10 and +10 sampling points.